Thermostat Diagnosis

Thermostat Diagnosis

Tools Required

J 24731 Tempilstick


Thermostat Test Procedure Using Tempilsticks





The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing (4).

1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat.

* J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F).
* J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).

2. Replace the coolant thermostat if it does not operate properly between this temperature range. Refer to Engine Coolant Thermostat Replacement (With LH8) (Service and Repair)Engine Coolant Thermostat Replacement (With LLR) (Service and Repair) .